| Summary: | Thesis (MScAgric)--Stellenbosch University, 2012. === ENGLISH ABSTRACT: The South African Ostrich industry was established more than 100 years ago. Despite appreciable
fluctuations and modifications in demand, the industry perseveres, with meat and leather as the
current primary driving force. Low and variable early chick survival is globally considered as a
major constraint in the industry. In spite of obvious welfare and production implications, research
findings concerning ostrich chick survival are scant. Four studies involving chick survival to 24
weeks post hatch were thus performed.
South African Black ostrich (Struthio camelus var. domesticus) data obtained from a commercial
pair-bred ostrich flock maintained at the Oudtshoorn Experimental Farm, South Africa comprising
10418 records were utilized to run a series of single- and multiple-trait binomial analyses using
either linear models (ASREML) or threshold models (Monte Carlo Markov Chain methods,
employing Gibbs sampling software) respectively. Suitable fixed and random effect models
together with variance and (co)variance components were derived from these analyses. Ostrich
chick survival to 24 weeks post hatch was low (28%) with a large environmental component. Preincubation
storage time only affected 0 to 3 week survival, while incubator had a significant effect
on cumulative survival traits to 24 weeks as well as on 13 to 24 week survival. Female chicks
outperformed males at 0 to 12 weeks, 0 to 24 weeks, 4 to 12 weeks and 13 to 24 weeks with
regard to survival. Hen age was significant for all traits except survival during the first week as well
as for survival from 13 to 24 weeks post hatch. All analyses exhibited comparable low heritability
estimates for all survival traits except for 0 to 1 week survival and 13 to 24 week survival (h2 = 0.12
and 0.10; m2 = 0.08 and 0.07 respectively) which demonstrated higher additive genetic and
maternal components when threshold models, using Gibbs sampling algorithms, were employed.
Neither moisture loss nor day of external pipping exhibited notable additive genetic correlations
with any of the estimated survival traits. Day-old chick weight demonstrated a low correlation with
early chick survival (rg = 0.24 ± 0.19) with heavier chicks tending to have a higher survival
probability. The effects of rearing method on early chick survival and growth were also
investigated. Comparisons between chicks reared and fostered by adult ostriches in a semiextensive
environment and chicks imprinted onto humans under an intensive system and between
regular human handling in an intensive rearing system and the standard farm protocol of an
intensive rearing system were made. No difference in the early chick survival to 3 weeks post
hatch of chicks reared by foster parents and those chicks imprinted onto humans was
demonstrated. At later ages, those chicks reared by foster parents outperformed human imprinted
chicks. Human imprinted chicks exposed to regular handling demonstrate an enhanced early survival when compared to chicks exposed to conventional rearing protocol in intensive systems.
The study is seen to provide guidance for further research on this topic. === AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse volstruisbedryf is meer as 100 jaar gelede gevestig. Die bedryf is volhoubaar,
ten spyte van ‘n fluktuerende aanvraag na volstruisprodukte. Vleis en leer is tans die produkte wat
die meeste tot die inkomste van boere bydra. Lae en wisselende kuikenoorlewing is ‘n belangrike
knelpunt in die bedryf. Navorsingsuitsette rakende kuikenoorlewing is skaars, ten spyte van
ooglopende welsyns- en produksie implikasies. Kuikenoorlewing tot en met 24 weke na uitbroei is
dus in vier afsondelike studies ondersoek.
Data van 10418 kuikens uit ‘n kommersiële broeipaargeteelde Suid-Afrikaanse Swart (Struthio
camelus var. domesticus) kudde op die Oudtshoorn Navorsingsplaas, Suid-Afrika is gebruik om
enkel- en meervoudige eienskappe met of liniêre modelle (ASREML) of drempelwaarde modelle
(Monte Carlo Markov Ketting metodes, met Gibbs monstering sagteware) te pas. Die metodes is
gebruik om toepaslike vaste- en toevalseffekte modelle saam met (ko)variansie komponente te
bekom. Kuikenoorlewing tot 24 weke na uitbroei was laag (28%), met ‘n groot
omgewingsbydraende komponent. Stoor van eiers voor pak het slegs kuikenoorlewing van 0 tot 3
weke beïnvloed, terwyl die broeikas wat gebruik is ‘n betekenisvolle invloed op kuikenoorlewing tot
24 weke ouderdom, sowel as op -oorlewing van 13 tot 24 weke gehad het. Wyfiekuikens het beter
oorleef as mannetjie kuikens vir oorlewing gemeet van 0 tot 12 weke, 0 tot 24 weke, 4 tot 12 weke
en van 13 tot 24 weke. Broeiwyfie ouderdom het ‘n betekenisvolle invloed op kuikenoorlewing in
die eerste week na uitbroei en van 13 tot 24 weke na uitbroei, gehad. Kuikenoorlewing was relatief
laag oorerflik, behalwe vir oorlewing van 0 tot 1 week en vir oorlewing van 13 tot 24 weke van
ouderdom (h2 = 0.12 en 0.10; m2 = 0.08 en 0.07 onderskeidelik). Drempelwaarde modelle met
Gibbs monstering algoritmes het hoër additiewe en maternale variansie verhoudings in vergelyking
met liniêre modelle aangedui. Genetiese korrelasies van vogverlies en die dag van uitwendige pik
met kuikenoorlewing was oor die algemeen onbeduidend. Dagoudkuikengewig is laag
gekorreleerd met vroeë kuikenoorlewing (rg = 0.24 ± 0.19), met swaarder kuikens wat oor die
algemeen beter oorleef. Die gevolge van verskillende grootmaak metodes op vroeë
kuikenoorlewing en -groei is ook ondersoek. Vergelykings tussen kuikens grootgemaak deur
volwasse volstruise as pleegouers in ‘n semi-intensiewe omgewing en kuikens grootgemaak deur
mense onder ‘n intensiewe stelsel en tussen kuikens grootgemaak deur gewone menslike
hantering in ‘n intensiewe grootmaak sisteem onder standard plaas protokol was bestudeer. Geen
verskille was gevind in vroeë kuikenoorlewing tot 3 weke na uitbroei, van die kuikens grootgemaak
deur volwasse volstruise en tussen die kuikens grootgemaak deur mense . By latere ouderdomme,
het die kuikens wat grootgemaak was deur volwasse volstruise beter oorlewing getoon as die
kuikens grootgemaak deur mense. Kuikens grootgemaak deur mense wat blootgestel was aan gereelde hantering het verhoogde vroeë oorlewing getoon in vergelyking met kuikens grootgemaak
deur konvensionele grootmaak protokol in intensiewe stelsels. Die studie kan dus beskou word om
leiding te verskaf vir verdere navorsing oor hierdie onderwerp.
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